The first heretic I encountered was an instructor who taught introductory philosophy at Brooklyn College. "There's no way to pass this course if you believe in God," he announced on the first day of class. My cloistered yeshiva life barely behind me, I found myself in 1972 sitting in the same classroom with girls and goyim, and an atheist for a teacher. The memory came to mind when I heard that another former Brooklyn College professor of mine, historian and Orthodox rabbi David Berger, was in Jerusalem. Berger, who will be assuming a new position at Yeshiva University this Fall, was here to lecture at a symposium entitled "Defining Heresy: The Shifting Boundaries of Religion" at the Institute for Advanced Studies at Hebrew University. Berger's presence at Brooklyn College was immensely reassuring. He was a modern Orthodox Jew (by which I mean strictly observant, yet seeking to engage with modernity). Whether he knew it or not, he was a role model for many of the yarmulke wearers on campus. Unlike the philosophy instructor, whose name I no longer remember, Berger wasn't all flash and no fire, but a scholar of substance. He came to class prepared and his lectures were lucid. To this day I've kept my notes from his courses on ancient and modern Jewish history. I MET UP with Berger, who is also a leading expert on Catholic-Jewish relations, intending to ask him about Pope Benedict XVI's decision to make it easier for a minority of Catholic priests who want to celebrate the Tridentine Mass to do so. This mass, recited in Latin, was the prevailing custom from 1545 until 1962. The Catholic mass is more than just a series of prayers; faithful participants believe they are literally experiencing Jesus's sacrifice. The problem with the Latin mass, from the Jewish perspective, is that it once contained a reference (removed by Pope John XXIII) to "perfidious [or faithless] Jews." The Good Friday liturgy of the Tridentine Mass includes, according to Abraham Foxman of the Anti-Defamation League, the following prayer: "Let us pray also for the Jews that the Lord our God may take the veil from their hearts and that they also acknowledge our Lord Jesus Christ. Let us pray: 'Almighty and everlasting God, You do not refuse Your mercy even to the Jews; hear the prayers which we offer for the blindness of that people so that they may acknowledge the light of Your truth, which is Christ, and be delivered from their darkness.'" Foxman argued that reciting this supplication would be "a body blow to Catholic-Jewish relations." BERGER TOLD me he still wanted clarification on whether the prayer would indeed be included. If it's in, he would prefer the courteous lobbying approach spearheaded by the International Committee on Interreligious Consultations, which had already sent a letter of inquiry to Walter Cardinal Kasper, the Vatican's emissary to the Jews. It was signed by AJCommittee's Rabbi David Rosen, Rabbi Richard Marker, an academic, and veteran Jewish leader Seymour Reich. Berger, who articulates his words in measured, thoughtful and precise phrases, isn't comfortable with the idea of telling Christians what to believe about their own religion. In a recent New York Jewish Week op-ed, he wrote: "While Christian revision of teachings that contain the potential of spawning anti-Semitism is very much the Jewish interest, Jews need to be cautious about making demands that can create resentment and backlash and even legitimize Christian demands for reciprocal revisions in Judaism." Berger went on to argue that the "imperative of self-defense allows Jews to pursue a carefully formulated argument that Christians should refrain" from proselytizing. But just where to draw the line, he says, is something to agonize over - not yell about. WHY IS the Latin mass important to Pope Benedict? It's because he wants theologically conservative Catholics, of which he's one, to feel spiritually at home in the Church. A tiny schismatic faction led by the late French archbishop Marcel Lefebvre split from Rome in 1988 because it felt the Church was pursuing a wide range of heretical reforms - jettisoning the Latin mass being just one instance. For the ultra-conservatives, making it easier to conduct the Tridentine Mass is too little, too late; while for theologically liberal Catholics the decision is seen as a capitulation to the Lefebvrists. Liberals worry that the Vatican is embarking on a journey that could reverse 40 years of innovation. Today's mass is recited in the vernacular, priests face worshipers, there is congregational participation and various forms of religious music are allowed. To add to his troubles, Pope Benedict has come under criticism from Protestants for proclaiming last week that there were "defects" in their beliefs. The Vatican holds that while Protestants are part of the "Christian community" they are separated from the true Church - meaning from direct lineage to Jesus's original apostles claimed by Rome. BERGER AND I didn't talk much more about the Latin mass. His being in town lecturing on heresy led to the subject of Chabad. His book The Rebbe, the Messiah and the Scandal of Orthodox Indifference is the most powerful polemic against what's become of the Lubavitchers. As Berger sees it, their theology is distinctly at variance with the established religious beliefs of Jewish Orthodoxy. Here's the rub: The Lubavitchers' beliefs are a problem for Berger precisely because he's a true believer himself. He takes to heart the Thirteen Principles of Faith, in which Maimonides (1135-1204) summarized Jewish dogma. Were Chabad not viewed by so many as "Orthodox," Berger would be less anxious about their inroads into Jewish life; the Lubavitchers would be just another schismatic group. The problem is that Chabad looks Orthodox, walks Orthodox, quacks Orthodox. I asked Berger why the Chabad issue hardly makes any waves in the Orthodox world. His answer was that the Orthodox delude themselves into thinking that only a minority of Chabadniks are messianic - when a majority is. To the extent that there is a minority in Chabad, it is the faction that worships the Rebbe as an outright deity. "The Orthodox are also insensitive to the key point that recognizing messianists as Orthodox rabbis legitimates this belief within Orthodoxy irrespective of the number of believers," he said. Faced by Chabad's extraordinary theological assault from within, Orthodox leaders pursue the path of least resistance. Their approach is to avoid acrimonious confrontation (I suppose they save that for gays, Russians who want to convert, the secular, and the other major streams of Judaism). Maybe, Berger surmised, the Orthodox tell themselves: This Rebbe-messiah business is a passing fad. Anyway, each Orthodox sect looks after its own interests, and there is no advantage in taking on Chabad. Conversely, the Orthodox world is interdependent. To openly challenge Chabad across the globe would be an undertaking of immense proportions and debilitating to Orthodox interests. So when Orthodox people see Chabad doing good deeds, working with drug addicts, feeding the hungry, providing low-cost day care and bringing kosher meals and holiday services to places off the beaten track, there is no incentive in asking: But in the service of what religion are they doing all this? No incentive that is - absent theology. Berger has argued that Orthodoxy forbids the belief that the Lubavitcher Rebbe, who died in 1994, will return to redeem the Jewish people. There is no Second Coming in Judaism. IT'S IMPOSSIBLE to detach Berger's efforts to sound the alarm in the Orthodox community about Chabad from his own Orthodoxy. What Berger is saying is that, even putting aside the Chabad issue, Judaism has a creed. And for him, Maimonides's Thirteen Principles best provide the parameters of Jewish faith, although reasonable believers have differed about the application, interpretation or inclusion of one or another of the Thirteen. Berger told me that while Halacha can be arrived at by consensus, dogma can't. You either accept that God dictated the Torah to Moses at Mount Sinai, or you don't; that He is incorporeal, or He isn't; that God knows everything we think, or He doesn't; that there is reward and punishment, or there isn't; that the Messiah will come, or that he is a myth; that there will be a resurrection of the dead, or that they will stay as they are. To be a genuinely Orthodox Jew, according to Berger, it isn't enough to "do"; one must also "believe" in the doctrine. Not surprisingly, there are other modern Orthodox scholars who disagree with Berger on the importance of Maimonides's Thirteen Principles. Marc Shapiro, a Judaic Studies professor at the University of Scranton, argues in The Limits of Orthodox Theology that Maimonides's principles never enjoyed universal acceptance in the rabbinic world - the implication being that even traditionalists can't agree on a clear expression of dogma. University of Haifa professor Menachem Kellner in Must a Jew Believe Anything? goes further in arguing that not only doesn't Judaism have a dogma; we shouldn't go down that road because it could create a future of mutually exclusive "Judaisms." IT'S HARD not to admire Berger's spiritual integrity and his fidelity to classical Judaism. I share his concerns about Chabad - not because they've shifted from Orthodoxy (so have I), but because they're starting to look too much like the competition. At the same time, I'm not comfortable with the idea of a Jewish catechism. My hunch is Berger realizes his brand of modern Orthodoxy, which insists on blending modernity and dogma, is not on the ascent. If anything, it seems to be losing ground - to the progressive streams, which have modified (or discounted) classical dogma, and to the ultra-Orthodox world which, arguably, emphasizes ritual over theology. There is, however, a larger issue at stake. It may well be that heresy is dead. Boundaries, as Prof. Kellner aptly cautions, would pave the way toward a world of "mutually exclusive Judaisms." And that's a disquieting prospect. Yet the demise of dogma is not just a setback for true believers like David Berger. It poses a challenge for the rest of us in defining the parameters - maybe not of the Jewish faith, but of Jewish civilization.